The invention relates to an apparatus for detecting the wearing of a seat belt assembly which is provided in an automobile or the like, and more particularly, to such an apparatus which prevents the failure of wearing a seat belt by producing an alarm when such failure is detected.
An automobile is usually provided with a seat belt assembly which is effective to restrain an occupant sitting on a seat against collision against a steering wheel in the event of an emergency. Such seat belt assemblies are essential to secure the safety of an occupant, who maybe legally obliged to wear it.
Generally an occupant couples a tongue plate with a buckle of a seat belt assembly and then extends its webbing around his body each time he gets into a vehicle, and uncouples the assembly by a reverse procedure when getting out of a vehicle. Because such operation is unfamiliar in routine life, there are occurrences that an occupant who is not accustomed to riding in an automobile frequently forgets to wear a seat belt assembly.
To accommodate for this, many automobiles are provided with a detector switch which detects the coupling between the buckle and the tongue plate of the seat belt assembly. A failure of wearing the seat belt assembly may be warned by energizing an alarm such as a warning lamp or buzzer for a given time interval if the detector switch indicates the absence of the coupling when an ignition switch is turned on or when an engine is turned on.
Considering an automobile which is provided with a passenger seat located alongside a driver's seat, if a driver gets into the automobile alone, a seat belt assembly associated with a passenger seat is obviously not worn, and according to the logic mentioned above, a warning will be given to a passenger who is actually absent. This would be a procedure which is much too troublesome. For this reason, in the prior art practice, the warning period has been limited to a predetermined time interval from the turn-on of the ignition switch or to a time interval from the turn-on of the ignition switch until either detector switch indicates the presence of a coupling.
However, when such limitation is employed, the following inconveniences can result.
First, if a driver gets into a vehicle after the predetermined time interval has elapsed from the turn-on of the ignition switch, there is no annunciation of a failure to wear the seat belt assembly. This would be the case when boarding after a period of warm-up or when a driver has turned the engine on, but then gets out and subsequently gets in again.
Second, if either occupant wears his seat belt assembly, the failure to wear the seat belt by another occupant cannot be annunciated. This would be the case when a driver has initially gotten into the automobile and has worn the seat belt assembly, followed by the boarding of another occupant.
It is an object of the invention to provide an accurate detection of the wearing of a seat belt assembly.